After a well has been drilled and casing has been cemented in the well, one or more sections of the casing, which are adjacent to formation zones, may be perforated to allow fluid from the formation zones to flow into the well for production to the surface or to allow injection fluids to be applied into the formation zones. A perforating gun string may be lowered into the well to a desired depth and the guns fired to create openings in the casing and to extend perforations into the surrounding formation. Production fluids in the perforated formation can then flow through the perforations and the casing openings into the wellbore.
Typically, perforating guns (which include gun carriers and shaped charges mounted on or in the gun carriers) are lowered through tubing or other pipes to the desired well interval. Shaped charges carried in a perforating gun are often phased to fire in multiple directions around the circumference of the wellbore. When fired, shaped charges create perforating jets that form holes in surrounding casing as well as extend perforations into the surrounding formation.
Various types of perforating guns exist. One type of perforating gun includes capsule shaped charges that are mounted on a strip in various patterns. The capsule shaped charges are protected from the harsh wellbore environment by individual containers or capsules. Another type of perforating gun includes non-capsule shaped charges, which are loaded into a sealed carrier for protection. Such perforating guns are sometimes also referred to as hollow carrier guns. The non-capsule shaped charges of such hollow carrier guns may be mounted in a loading tube that is contained inside the carrier, with each shaped charge connected to a detonating cord. When activated, a detonation wave is initiated in the detonating cord to fire the shaped charges. Upon firing, the shaped charge emits sufficient energy in the form of a high-velocity high-density jet to perforate the hollow carrier (or cap, in the case of a capsule charge) and subsequently the casing and surrounding formation.
An issue associated with use of shaped charges is how effective the shaped charges are in penetrating the surrounding casing and formation. Most conventional shaped charges used in wellbore environments employ powdered metal liners. However, an issue associated with such powdered metal liners is reduced impact pressure, which can cause reduced penetration effectiveness.